1. Field of the Invention
This invention relates to a colored image reading apparatus to be used in a copying apparatus or a facsimile for copying or reprinting original documents or the like, and more particularly to an apparatus for scanning the surface of an original relatively in two directions and reading the information carried on the surface of the original as four types of color information, i.e., black, red, blue and white.
2. Description of the Prior Art
In recent years, there have been proposed image formation apparatus in which the information of an original is read in bit units by a light-receiving element such as a CCD and converted into electrical signals thereby and digitally recorded in accordance with the converted signals. Of the information of ordinary originals such as documents, four types of color information, i.e., black, red, blue and white, are most important and highest in frequency of appearance.
The reading apparatus of the prior art uses, as the means for reading an original in bit units and discriminating between black, red, blue and white, a method of optically color-resolving the information of the original into three components R, G and B as by a color mosaic filter or a beam splitter and reading them by a light-receiving element such as a CCD. With such a method, however, whatever minute mosaic filter is used, the color-resolved components R, G and B are image information of different locations on the original and a reduction in the resolving power during the reading occurs. There is the further problem that the processing circuit for the signals R, G and B put out from the CCD is complex.
On the other hand, a method of color-resolving the information of an original into components R, G and B by the use of a dichroic mirror or a prism suffers from the disadvantages that it requires three CCDs, that the space required for them is large and that it requires a complex optical system.